Control apparatus for hydraulic systems



March 24, 1953 c, s, YlNGsT 2,632,459

CONTROL APPARATUS FOR HYDRAULIC SYSTEMS Filed Dec. 11, 1947 2 SHEETS--SHEET 1 I 291 1 27A I H a Match 24, 1953 s, Y|NG$T CONTROL APPARATUS FOR HYDRAULIC SYSTEMS 2 SHEETSSHEET 2 Filed Dec. 11. 1947 control valve 26. It is also to be noted that each end portion of the valve 26 is connected in a conventional manner to a line 3| which discharges into the supply tank 2| by way of a throttle 32 which is adapted to be manually or automatically operated for the purpose of varying the traversing speed of the piston 29. It is obvious that when the control valve piston 33 is moved to the right, it will be effective to connect the power line 22 with the line 36 of the power cylinder, and also to connect the power cylinder line 28 with the discharge line 3|, all to the end that the piston 29 will be forced toward the right-hand end of the power cylinder.

For actuating the control valve piston 33, a conventional type of four-way valve 34 is connected in the system. More specifically, the valve 34 is adapted to be actuated by means of an appropriate mechanism 35 connected with the power piston 29. Also, the valve 34 is connected directly with the power line 22 by way of a line 36. Therefore, when the valve 34 is actuated in one direction, it will be efiective to supply fluid from the power line 22 directly to the right-hand end of the control valve 26 by Way of a line 31. Such a flow of fluid will, of course, force the piston 33 into the position illustrated in Fig. 1. During this portion of the control valve cycle, oil from the left-hand end of the control valve 26 may escape through a line 38 which is connected to a discharge line 39 by way of the valve 34. If desired, a dwell throttle 40 may be provided in the line 39 for controlling the dwell of the traversing mechanism. The free end portion of the line 39 is connected with the tank 2|. Obviously, when the four-way valve mechanism 34 is shifted in the other direction, it will be effective to reverse the functions of the lines 31 and 38 to the end that the control valve piston 33 will be shifted toward the right-hand end portion of the control valve cylinder, thereby reversing the direction of movement of the power piston 29.

If desired, various auxiliary hydraulic mechanisms may be operated from the main power line 22. For example, in Fig. 1 there is illustrated a second hydraulic cylinder 4| which may be used for actuating work-clamping mechanisms. Such a cylinder 4| may be provided with the usual piston 42 which is actuated by fluid presdirectly to the power line 22 by way of a line 46. Also, the valve 45 may be provided with a discharge line 41 for delivering the exhaust fluid directly to the tank 2|.

Figs. 2 to 11, inclusive, particularly illustrate the present dump and relief valve mechanism which is designated by the numeral 25 of Fig. 1. In a preferred form of this dump and relief valve mechanism, it is constructed as a single unit, contained in a suitable housing 48. Referring particularly to Fig. 2, the housing 48 is provided with an inlet conduit 49 having the line 23 from the large-capacity pump |5 connected directly thereto. Also, the small capacity pump line 24 is adapted to be connected directly to an inlet conduit 50 provided in the housing 46. A vertically disposed outlet passage 5|, provided in the housing 46, is adapted to have the main power line 22 connected directed therewith. Still referring to Fig. 2, the housing 48 is provided with a return conduit 52, to which the return line 53 4 is connected for the delivery back to tank 2| of all of the pumped fluid in excess of that which is being passed into the system by way of power line 22.

Referring particularly to Figs. 2 and 3, the housing 48 is provided with a vertically disposed valve-receiving bore or chamber 54, in the top portion of which is slidingly received a valve 55 which is provided with a flange 56 at its upper end. In opposition to said flange 56, the bore 54 has a shoulder 51 which serves to limit downward movement of valve 55 under the force of a pair of coil springs 58, 58, the lower portions of which engage the valve 55. The upper portions of the springs 58, 58 engage an adjusting screw 59 which is threadably received within a plug 60 screwed within the upper portion of the bore 54. The screw 59 is adapted to vary the pressure of the springs 58, 58 as the same is adjusted within the plug 60.

The valve 55 is provided with a central hollow downwardly opening portion 6| which, in the position shown in Fig. 3, communicates directly with an annular bore groove 62 by way of radial conduits or ports 63, 63 and a valve groove 63 whose width is that of the land or ungrooved bore portion between bore groove 62 and an upper bore groove 82. This groove 62 is provided about the bore 54 and communicates directly with a horizontal passage 64 which, in turn, is connected directly with the inlet passage 56 to which is connected the oil line 24 from the low capacity pump |6 (see Fig. 6). From this, it is to be understood that fluid from the low capacity pump is adapted to be delivered into the valve bore space below the valve 55 by way of the passages 59 and 64, grooves 62 and 63 and the radial conduits 63.

Referring particularly to Figs. 2 and 6, it is to be noted that the oil inlet passages 50 and 64 from the small capacity pump |6 are connected by way of a relatively restricted orifice 65 to the outlet passage 5| that serves the power line 22. From this, it will be understood that some of the fluid under pressure coming from the low capacity pump l6 will pass directly into the outlet passage 5| and power line 22, but at a pressure normally somewhat lower than that prevailing within the passage 50, because of the restricted character of the orifice 65.

Referring again to Fig. 3, there is slidingly disposed within the lower portion of the valve bore 54, a second or control valve 66 in the form of a hollow piston, whose skirt portion extends downwardly within the bore 54 into abutting relation, in the valve position of Fig. 3, with spaced legs 69, 69 that are provided by a, plug 61 which closes the lower end of bore 54. Figs. 10 and 11 illustrate the closure plug 61 which is adapted to be threaded as at 68 directly into the lower portion of the bore 54. Provided upon this screw plug 6'! are the spaced leg portions 69, 69 which are adapted for engagement with the valve 66 in the manner as illustrated in Fig.3. Surrounding the valve bore 54 and adapted to communicate therewith in the zone occupied by the valve 66 are three relatively large vertically spaced annular grooves 10, H and 12. The upper groove 70 communicates directly with the inlet passage 49, which as hereinabove noted, is connected with the large capacity pump |5 by way of the line 23. Also, the inner hollow portion 66' of the valve 66 communicates, in the position shown in Fig. 3, directly with the annular groove 16 by way of aplurality of ports 13, 13. Thus,

5'3: fluid vfrom: Lthelarge capacity pumpzzi 5 has directs access to -the interior portion 'fifi of the valve? ssri'i: by -way of the annulanigroove :70 and the valve portsi l3;' 731 Refer-ring particularly *to Figs: 2,3 and 5,) it ism 5 to .be noted thatthe intermediate annular groove .1 I I communicates directlyllwiththe horizontally" disposed: passage -52 whi'ch in itu rn is connected to the tank 2 l by way of the:return' line 53. L the: position of valve GBJshown :by Fig 3,:it presentsa reduced diameter;portion i BE' of its skirt inzopposed relation to the bore groove 'lli The latter-was" shown in= Fig-i -3, *is separated 1 from the upper bore groove by a relatively narrow-land I 812 Thus,- although the valve 'fifi i's positioned in 3 to::cut off anyaccess'of the :pumped oilt to -thereturn-groove I"; it will beevid'ent-that a slight upward movement of -valve fifi from -its illustrated lowermost position will plac'e the 'return gro'ove I in'* full communcation with the groove 'lfi'i- -and thereby cause the fluid "comin'gfrom' th large-pumpL- l5 to b= returned toth" tank 2|.

Refer-rmg now; to Figs'wZ, 3 and 4, -'it i is to be understood thatthe -1ower Zannu1ar groove- 1 2 communicates -;directly with a horizontally dis- 1 posed passage -14-;-one'-end'portion ofw-hich' is connected directlywith 'the vertically'- disposeddi's'charg conduit 5 l by' way of a shortcross pas sag'e' l Alsoy it is to be fu'rther understood that: isannular groove l2 communicates .directlylwitl nth'e sinner .-portion*;15;;of1 the closure plug:- G'Hby yirtue;of the factilthat the-plug; legs 69, :59 arexspaced apartq from-each other;

eier a:panticul l itolif es; 8 a d.;9, vthere is provide within-,the; lowenhollow portion 66' of the valvefifi; a check valve 16 which is pro-\ videdtwith -a painoi spaced legs 11, vll-between whichis mounted a cross pin 18. 1. Associated with thefchefclg valve .16 is ,a vcoil spring 19; one end oflwhich is fastened to'the cross pinfl18and the other endj of which is'fastened tola second cross pin "801"" Thus'the'spring" W'serves'to hold valve l6 yieldingly against its annular seat 88which is providedbythelowerend ofthe valve'66. This second crosspin 80' is mounted upona shoulder" portiontifll of" the" valve" 66 It is obvious that when theche'ck valve' 'l fii's in thnlosed position shownbyFig. 3, it ,willi'prevent any new "of'fiuid from the lowerportion'of *the bore"54 from"enter= ing the hollow portion of the valve 1 66.

Referringparticularlyto lfiigs. 2, 3, 5 and '7, it is to-befnoted that the upperportion" ofthe bore 54*i's provided with? the "annular groove'82 which communicates directly with a transverse passage 83-Which in turn is connected with" a vertically disposed; passage 84'. Referring particularly to Figsii2 'andf5jit "will be-"noted that this vertical passage" a l communicates-witl1 the return -'pas"- sage 52; so-'- that fiuid from the sma-ll pump 1 6" that reache's'the groovei 82--and'-passage '83Will ultimatelyffind its way back "into the tank 2|. However, -as"shown= in Fig;- 3, the groove 82 "is norm-ally'4b1o cke'd oif by'valve 55 from" any? access of' fljuid theretofl In? the f' operation -of "the"present system; "let it be assumed" that the'large'pump l 5"has"a' capacity of :ejieyen and one half gallons per-iminute," while the' low capacity pump [6 hasa capacity'ofone" and one half gallons perminutefthusgiving a 7 combined pump capacity of thirteen gallons P ri" minute.

Assuming that the various elements :of the dump; and relief va1ve"25\aredisposed in the posi-g tions shown inFig': 3 and that the throttle 321s wide op'en when the system isiinitially placed:- op'eration, i-t 'isli to'be understoodiithat:oil from the small capacity pump (i -will"be delivered into the bore 54 between valves 55 an'd 66',' by"way.f0f- 1 the passages Jand 64, and thelradi'al' parts 63,1 63". This oilwill be effective to buildup a statics: oil pressure between the'valves and fifi lwhich t pressure will be efictive to -urge thesetwo valvesaz in opposite-directions; thereby .foroing :the" valve 55 against the springs 58 58g' andithevalve 665.5 again'st'thelegs'69; 69 ofth'screw plu'g 611 D11 to the existence of the orifice between' the? passages 50 and '5 I; the oil pressure in the space between the valves "55 and 66- will ''beinitially greater than that existing Within the outlet='pas'- sage" 5l and -its connecting power line 22.

Under" these" open throttle conditions; tli oil n from'the large capa-city"pump**I5isadapted reach-"theinterior-space Bit-"of valve fifi by-way o the" passage 49,- the+annular groove '10, and-the valve"ports--'l3, 13.- As' thus delivered into-*th ii hollow portion 56 of the valve 66; the "oil from the largecapae-ity pump will immediately force? the check -valve 16 open and-flowinto thepassa'ge 14" by way of theinterconnectingannular groove 122' Thus,- the -oil frombothpumps'-'l5"'and' 16 is-full-y available, whim-throttle=52 is openedfor rapid traverse,--for flow' into outlet-passage 5 supplythe demands'of'poweriiri'e 22; Although. theoilfrom the la'rge capacity p-um'pwill have a tendencyto lift the valve fifi' wi-tliin 'th'e' bore -5 lg it willbe' understoodthat whenev'enthe-oil de"'--- mand, as determined by the throttle32fiis large,

the back pressure within thepassage 5l andthe line 22 "will belo'wered and thus-"by virtue'of-the'; orifice 65; the oil pressureefie'ctive against the I upper portionof the valve lie-Will begreater than that which'tends to move said-valve upwardly.

However,- with throttle 32 moved; for slow trav erse purposes to a position wherethe oil'demand becomeslessthanthirteen gallons'per'minute' (the assumed combined capacity of the two pumpslfit will be obvious that theback -pressure withinthe" line 22 and the passage" 5l' will tend toincreasei-" thus increasing the oil pressure wi-thin--the-upper-=- portion of the'bore or chamber54 andwithin ther hollow portion-66'-of theva1ve66'r As-thisback" pressure increases; it will scene-enveto shift the valve 55 upwardly within the-bore 54 and'againstri the force of the springs 58, 58 and thereby tend to cut ofi "communication betweenthe valve. V groove 63' and'theoi1 supply groove62f= Of course ,1 the springs 58; 58"are adjusted to a predetermined or desired setting by means of the adjustingscrew"'-f 59 ashereinabove noted.

When communication has" beencut .off betweenthe valve groove 63"and the groove 62', 'nofure" the'roil can gain entrance into" the upper"por-" tion of the bore or"chamb'er-"54"""and therebyk'f increase the pressure- 'withinthis" portion Ofthj bore. However, as the back pressure increasesi'f within the main line '22 and the passage 5l, iti': will soon 'be great enough to move the" valve'66"" upwardly within the bore54 andfof'course, this upward movement of the valve'fidcann'otj occur" until the predetermined force "of thefsprings 58; 58 is overcome, for the liquid betweenfthe valves 55 and 65' is substantiallyincompressible;" This initial upward movement of the valve' 66 will cause valve 55 to raise in synchronism there- I with, thus placing the valve groove 63' of valve 1 55 in partialcommunication with the'annularg groove 82 so that the oil pressure'betweenvalves" 55 and 66 is slightly relieved by way of the eon-=1 du'its 83584 and-52 Also; this upward movement of valve 66 will be efiective almost immediately, to put the large pump delivery passage 49 in partial communication with groove H, return passage 52, and dump line 53, to the end that less than the total capacity of the large pump 45 is delivered to the main line 22, thus maintaining a constant predetermined oil pressure in the system. It should be understood that as soon as the oil between the valves 55 and 66 is so relieved, the springs 58, 58 will force the valve 55 down again thereby maintaining a constant pressure upon the valve 66.

If the above slight upward movements of the valves 55 and 66 are not sufiicient to maintain a constant liquid pressure within the system, the valves 55 and 66 will continue their upward movements until all of the flow from large pump is diverted to the return line 52, 53 and a greater portion of the oil between the two valves isrelieved by way of valve groove 53 and bore groove 82. At this juncture, the check valve 16 will close under the biasing pressure of its spring 19 and the force of the fluid within the lower portion of the valve bore 55. Again, as soon as the oil is relieved between the two valves by way of groove 82, the valve 55 will tend to shift downwardly under the force of its springs. It should be realized that when the entire capacity of the large pump i5 is so dumped, only one and one-half gallons of the oil per minute, or the assumed capacity of pump [5, is delivered to the main line 22, thus maintaining the oil pressure constant Within the traversing system.

If, however, the above relieving and dumping action is not suificient to maintain a constant oil pressure, the valve 66 will be further elevated under the pressure of the oil in the lower portion of the bore 54, thereby again raising valve 55 to its flow-diverting position where some of the oil from the small pump is will enter the groove 82 and pass by way of conduits 83 and 84 to the lower end of valve bore 54. In the ensuing further rise of valve 66, the excess of oil thus diverted to the lower end of bore 54 escapes into return groove H by way of an exterior groove 86 provided at the lower end of valve 66. Thus, there will be now building up of oil pressure within the system, even when the latters demands for oil are well below the capacity of the small pump l6.

From the above, it should be understood that the dump and relief valve 25 maintains a constant machine oil pressure within the line 22 at all times regardless of the oil demand and the amount of this pressure is determined by the setting of the springs 58, 58. It should be further understood that the pressure of the oil trapped between the two valves 55 and 66 is, during the operation of the system under load, kept substantially constant, as determined by the setting of springs 58, 58, by virtue of the fact that this oil is constantly relieved through the bore groove 82 and valve groove 63 as the valve 66 raises in response to positive fluctuations in the back pressure of the oil in the line 22.

In other words, once the valve 55 has been raised, under the force of oil from the small capacity pump, so that the valve groove 63' no longer communicates with the chamber or bore groove 52, any slight positive or negative fluctuation in the liquid back pressure above or below the predetermined value will be effective to shift the valve 55 slightly upwardly or downwardly thereby to maintain the liquid pressure within the liquid-operated motor system substantially at the predetermined value at all times within the range of desired normal flow requirements of the system. The presence of the restricted orifice 65 is effective to maintain the valve 66 in its illustrated or nonflow-diverting position until the back pressure within the system reaches the above noted predetermined value.

From its raised position, whenever the back pressure in the system tends to decrease, due to a greater oil demand, the valve 66 will shift downwardly, thus permitting a greater amount of oil to be delivered from the pumps l5 and Hi to the line 22, but always at the same constant predetermined pressure.

In the event that the auxiliary or clamping cylinder 4| is operated during the operation of the power cylinder 21, it will be clear that the machine oil pressure will be substantially unaffected for the reason that the two valves and 66 will automatically adjust themselves to produce a greater flow of oil into the line 22 in immediate response to any tendency of the pressure to drop within line 22.

As hereinabove described, the present control apparatus has two pumps I5 and I6 associated therewith, but it is to be understood that such an arrangement of valves will also function efliciently if only one pump is connected in circuit therewith. For example, a large capacity pump may be provided with one output line which may be connected to the valve housing inlet 50, and another to the housing inlet 49. By this arrangement, a single pump having, for example, an output of thirteen gallons per minute could be effective to operate the system hereinabove described in substantially the same manner as effected by the two pumps I5 and Hi. In this connection, it should be understood that various settings of the springs 58, 58 may be made and the orifice may have its diameter altered in order properly to accommodate the valve for use with different system requirements.

I claim:

1. Control apparatus of the class described for delivering continuously pumped fluid under a predetermined substantially constant pressure to a variable demand hydraulic system, with diversion of the undemanded pumped fluid to the pump supply, said apparatus including a valve casing having two intakes for the pumped fluid, a single outlet by which the pumped fluid is delivered to the system, a return connection through which undemanded pumped fluid is diverted to the pump supply, and a restricted orifice connecting one of said intakes to said outlet, a valve bore in said casing, a piston valve movable in said bore and adapted in one position to pass fluid from the other intake to said outlet and in another position to divert said fluid to said return connection, a second piston valve disposed in said bore in spaced relation to the first valve and maintained normally by spring pressure in a position to connect the space between said two valves with said first mentioned intake, for holding said first valve in non-diverting position, until the systems back pressure prevailing in said space increases to a predetermined value, whereupon said second valve is moved to disconnect said space from said first intake, thereby relieving said space sufli-ciently for the systems back pressure effective on said first valves other end, to move same into fluid diverting position.

2. Control apparatus as claimed in claim 1, having one fluid intake of higher capacity than the other, said higher capacity intake being associated with the first-mentioned fluid diverting valve.

3. Control apparatus as claimed in claim 1, wherein the fluid trapped in the space between the two valves communicates the movement of the first valve to the second valve.

4. Control apparatus as claimed in claim 1, wherein continued movement of the second valve vents the fluid trapped in said space to said other end of the first valve.

5. Control apparatus as claimed in claim 1, wherein continued movement of said first valve vents the fluid effective on its said other end into said return connection.

6. A valve mechanism of the class described comprising a valve casing having two intakes for pumped fluid, a single outlet port for delivery of demanded portions of the pumped fluid, a return connection through which undemanded portions of the pumped fluid are diverted to the pump supply, and a restricted orifice connecting one of said intakes to said outlet, a valve bore in said casing, a piston valve movable in said bore and adapted in one position to pass fluid from the other of said intakes to said outlet and in another position to divert said fluid to said return connection, a second piston valve arranged in said bore in spaced relation to the first valve and maintained normally by spring pressure in a position to connect the space between said two valves with said first mentioned intake, thereby to hold said first valve in nondiverting position until the back pressure of the demanded pumped fluid prevailing in said space increases to a predetermined value, whereupon said second valve moves to disconnect said space 10 from said first intake, thereby relieving said space sufliciently so that the demanded fluids back pressure effective on said first valve's other end moves the same into fluid diverting position.

7. A valve mechanism as claimed in claim 6, having one fluid intake of higher capacity than the other, said higher capacity intake being associated with the first mentioned fluid diverting valve.

8. A valve mechanism as claimed in claim 6, wherein the fluid trapped in the space between the two valves communicates the movement of the first valve to the second valve.

9. A valve mechanism as claimed in claim 6, wherein continued movement of the second valve vents the fluid trapped in said space to said other end of the first valve.

10.A valve mechanism as claimed in claim 6, wherein continued movement of the first valve vents the fluid efiective on its other end into said return connection.

CYRUS S. YINGST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,982,711 Vickers Dec. 4, 1934 2,074,618 Roeder Mar. 23, 1937 2,102,865 Vickers Dec. 21, 1937 2,404,102 Schultz July 16, 1946 2,420,890 Mac Dufi May 20, 1947 2,429,489 Roth Oct. 21, 1947 

